Wash tool method for subterranean wells

Abstract

The disclosure relates to an improved tool and method for effecting the washing of sand or particulates from casing perforations and channels in production formations in subterranean wells. The tool employed comprises an outer body suspended from a first tubing string and having vertically spaced seals in engagement with the casing wall above and below the set of casing perforations to be washed. Radial wash ports are provided in the outer body between the annular seals. An inner body, carried by a second tubing string is inserted within the first tubing string and outer body and effects a sealing engagement with the bore of the outer body at a location below the radial wash ports. Washing fluid is then introduced into the well through the annulus defined between the first and second tubing strings and the sand laden washing fluid is returned to the well surface through the bore of the inner body and the connected second tubing string.

We claim: 
     
       1. The method of washing casing perforations and connected formation channels of a subterranean well comprising the steps of: (a) inserting an outer tubular body into the well on a tubing string, said outer tubular body having radial ports alignable with a selected set of casing perforations, an open bottom communicable with the casing bore, annular sealing elements engaging the well casing above and below the said radial ports, and a radial bypass port disposed above said annular sealing elements;   (b) sealing the annulus between said outer tubular body and the casing above all casing perforations;   (c) inserting an inner tubular body having an open bottom bore within the outer tubular body on a second tubular string, a continuous annular passage thereby being defined between said outer and inner tubular bodies and said outer and inner tubing strings, the bore area of said inner tubular body being substantially less than the area of the annular passage;   (d) effecting a seal between the bottom end of said inner tubular body and the bore of said outer body at a position axially below said radial ports;   (e) circulating washing fluid downwardly through said annular passage, thence outwardly through said radial ports and through said casing perforations and said formation channels, thence around the exterior of the casing, and thence upwardly through the casing bore and the interconnected bore of the inner tubular member and its tubing string to the surface of the well; and   (f) maintaining said port open during step (a), and closing said bypass port during step (c).   
     
     
       2. The method of claim 1 wherein said outer tubular body has radial bypass ports disposed above said annular sealing element and having an axially slidable valve positioned above said bypass ports during step (a), plus the step of moving said axially slidable valve downwardly to a closed position during the insertion of the inner tubular body in step (c). 
     
     
       3. The method of claim 2 plus the step of withdrawing the inner and outer tubular bodies from the well, the inner body being moved in advance of said outer tubular body to shift said axially slidable valve upwardly to its open position above said bypass ports.